JPS63205616A - Optical fiber star coupler and its production - Google Patents

Abstract

PURPOSE:To prevent breakage in coupled parts and fluctuation in connection loss by integrally forming plural 3dB optical couplers without having coupled parts at all. CONSTITUTION:An optical transmission path consisting of an input 100 fused and stretched part 111(c-b) fused and stretched part 122(c-a) fused and stretched part 134(c-a) output 107 is formed of a piece of continuous optical fiber. All of the optical transmission path consisting of the fused and stretched part 111a fused and stretched part 121(c-b) fused and stretched part 131(c-b) output 102, the transmission path consisting of the fused and stretched part 121a fused and stretched part 132(c-b) output 104 and the optical transmission path consisting of the fused and stretched part 122b fused and stretched part 133(c-a) output 105 are formed of a piece of the continuous optical fiber. Namely, the respective fused and stretched parts 111, 121, 122, 131-134 are all coupled without having the coupled parts formed by working. The breakage in the coupling points and the fluctuation in the branching ratio by the connection loss are thereby prevented.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an optical fiber star coupler.

More specifically, the present invention is capable of branching an optical signal propagating through one transmission path into multiple transmission paths, especially three or more transmission paths, or branching an optical signal propagating through multiple transmission paths into one transmission path. The present invention relates to a new configuration of an optical star coupler that joins a transmission line of the optical star coupler, and a method of manufacturing the same.

Conventional technology, the so-called star coupler, has the function of branching an optical signal propagating through one transmission line to multiple transmission lines at the same time, and is useful for constructing optical communication systems such as wired TV (CΔT■) using optical cables. is an indispensable optical component. In particular, optical fiber star couplers formed from optical fibers are easy to couple with optical fibers, which are extremely widely used as optical transmission lines, so they have many opportunities to be used in the development and installation of various optical systems. be.

FIG. 4 is a diagram schematically showing the configuration of a conventionally known general optical fiber star coupler.

The fiber optic star coupler shown here has input 4
It was created with the intention of equally branching the optical signal incident from 0 to 8 outputs 51 to 58, and 7
It is constructed by coupling two 3 dB couplers 41 to 47. As shown in FIG. 4, the input 40 is an input to a coupler 410, the output of the coupler 41 is coupled to the next stage couplers 42 and 43 at coupling points 42a and 43a, respectively, and the outputs of the couplers 42 and 43 are further coupled to the couplers 42 and 43 of the next stage. Connection point 44 is connected to the input of the third stage coupler 44, 45, 46, 47.
a, 45a, 46a, and 47a. Outputs 51 to 58 of each of the couplers 44, 45, 46, and 47 serve as star couplers. Note that the optical signal injected into this star coupler is attenuated by 3 dB at each coupler, so the output is 5 dB.
The light intensity appearing at 1-58 is reduced by at least 9 dB.

Problems to be Solved by the Invention By the way, since this star coupler is constructed by coupling the seven optical fiber couplers 41 to 47 by fusion splicing as described above, the splice loss at each of the coupling points 41a to 47a is reduced. Occur. This means that not only does the attenuation of the optical signal in the star coupler increase, but also that the optical output of each of the outputs 51 to 58 also varies due to variations in the unavoidable connection loss at the coupling point.

In addition, in the actual joining work for producing the star couplers as described above, 30 cm are required before and after each of the couplers 41 to 47.
Extra length fibers 41b to 47b of m or more are required. Even after the star coupler is completed, the extra length fibers 41b to 4
Since 7b remains, it goes without saying that this impedes miniaturization of the device using the star coupler, and furthermore, the extra length of fiber 4
There is also the problem that breakage is likely to occur in the vicinity of the joints due to the load placed on the joints 421-47a by 1tl-47b.

Furthermore, in order to fabricate the conventional optical fiber star coupler as described above, it is necessary to fabricate seven 3 dB couplers with uniform characteristics in advance.

FIGS. 5(a) to 5(C) are diagrams illustrating the structure and manufacturing method of this conventionally well-known optical fiber coupler. That is, as shown in FIG. 5(a), the protective coating was first removed to leave only the core 84 and cladding 85.
The optical fibers 81 and 82 are arranged in parallel in close contact with each other. Subsequently, as shown in FIG. 5(b), the central portions 83a of the optical fibers 81 and 82 are heated to melt and integrate the two at this position. Further, the optical fiber 81. is heated at the same location so that the optical fiber remains in a softened state.
Apply tension to 82. Then, at the welded portion 83b described above, the optical fibers 81 and 82 are extended, and the cores 84 approach each other, so that propagating light mutually leaks between them.

In this way, an optical fiber coupler as shown in FIG. 5(C) is obtained, in which the welding/stretching section 83b serves as a light mixing/branching section.

FIG. 6 is a diagram schematically showing the configuration of an apparatus disclosed in Japanese Patent Application No. 59-88168 as an apparatus for manufacturing the above-mentioned optical fiber coupler.

This device is a device for manufacturing an optical fiber coupler by fusing and stretching two optical fibers at the center, and includes a pair of fixing devices 93a for fixing each optical fiber 91 and a predetermined section of 91. -93b.

94a-94b, and a pair of stretching tables 95a having the function of positioning the fused/stretched portion of the optical fiber and applying tension to the optical fiber near the center of the optical fiber 92 fixed thereto. , 95b.

That is, the fixing devices 93a-93b and 94a-94b respectively sandwich the optical fibers 91 and 92, and enable tension to be applied by stretching tables 95a and 95b, which will be described later. The stretching tables 95a and 95b have optical fibers 91.
A horizontal position adjustment device 97a comprising two pins 96a196b provided at a spacing such that the pins 92 are in close contact with each other at the center.
, 97b and horizontal position adjustment devices 97a, 97b are vertical position adjustment devices 98a that sandwich the optical fibers 91, 92 in a direction perpendicular to the plane of the paper and position them in a direction perpendicular to the plane of the paper.
, 98b, and optical fiber temporary fixing devices 99a, 99t.
l is provided for each.

In this device, first, two optical fibers 92 whose coatings have been removed for a predetermined length x-x are fixed to optical fiber fixing devices 93a-93b and 94a-94b with relatively weak tension, respectively. The optical fibers 91,92 are further held by stretching tables 95a, 95b near the center of the fixing devices 93a-93b, 94a-94b. That is, the horizontal position adjustment devices 97a' and 97b control the stretching table 9.
The optical fibers 91 and 95 are brought into close contact with each other in the same plane as the surfaces of the optical fibers 91 and 95b, and are further positioned by vertical positioning devices 98a and 98b so that the optical fibers 91 and 92 are not twisted. The optical fibers 91 and 92 are fixed in this position by temporary fixing devices 99a and 99b, and in this state, the center portions of the optical fibers 91 and 92 are fused by a heating device (not shown). Subsequently, while continuing to heat the optical fibers 91 and 92 to such an extent that the softened state is maintained, a force is applied in a direction such that the stretching tables 95a and 95b are separated from each other to perform stretching. In this way, an optical fiber coupler as shown in FIG. 5(C) is manufactured. ``The manufacturing operation of the conventional optical fiber coupler as described above is an extremely precise operation. That is, for example, the maximum force applied to an optical fiber for fixing or stretching is several grams per fiber, and the length of the fused/stretched portion of the optical fiber is approximately several mm.

Furthermore, factors such as twist of each optical fiber also affect the characteristics as an optical fiber coupler. This level of load or accuracy is at a level that easily changes due to the friction or friction of each member constituting the device, and therefore, various adjustments to each optical fiber are extremely delicate. It is virtually impossible to make such adjustments only by operating the equipment; in reality, a predetermined amount of light is injected from one end of the optical fiber being fabricated, and the light is monitored at the other end while being fused or stretched. By doing this, a product with uniform characteristics was obtained.

Therefore, it takes at least 2 hours to fabricate one coupler, and it takes about 5 hours to perform six connection operations and reinforce the coupling portions in order to assemble seven 3-dB optical couplers in multiple stages. Therefore, it took about two days to manufacture the entire optical fiber star coupler.

For these reasons, the optical fiber couplers currently on the market are extremely expensive at 1.5 to 2 million yen for 1-8 branch types, and metal cables using such elements should be replaced. It was not possible to make the optical system basolaterally practical. Furthermore, there are problems in practical use in terms of reliability and variation in characteristics, which has been a major problem in constructing optical communication systems such as optical CATV.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to achieve far higher performance in terms of characteristics, reliability, space utility, productivity, and cost. An object of the present invention is to provide a novel optical fiber type star coupler having the following features and a method for manufacturing the same.

Means for solving the problem, that is, according to the present invention, the input of the first stage optical coupler is an input from the outside, and the output of the first stage optical coupler is connected to the second stage optical fiber. is the input of the coupler,
The output of the first-stage optical fiber coupler is the input of the i+1-th stage optical fiber coupler, and the output of each n-1-th stage optical fiber coupler is the output to the outside, and the overall number of branches is 2n stages of optical fiber star couplers, each of the optical fiber couplers having a first
The optical coupler is formed by melting and drawing the side surface near the end of the second optical fiber in close contact with the side surface of the optical fiber strand, and each of the continuous optical couplers is formed by one continuous optical fiber. An optical fiber star coupler is provided, characterized in that the optical fiber is commonly used as the first optical fiber or the second optical fiber.

Further, as a method for manufacturing the optical fiber star coupler as described above, according to the present invention, the input of the first-stage optical coupler is an input from the outside, and the output of the first-stage optical coupler is an input from the outside. This is the input of the second stage optical fiber coupler, and the output of the first optical fiber coupler is the i+
It is the input of the first stage optical fiber coupler, and the n-1th
A method for manufacturing an n-1 stage optical fiber star coupler in which the output of each optical fiber coupler serving as a role is an output to the outside and the total number of branches is 2'', the method comprising: A side surface near the end of a second optical fiber is tightly fixed to a first position on the side surface, and the first and second optical fibers are attached on the same side with respect to the first position. The side surfaces near the ends of the third and fourth optical fibers are brought into close contact with the respective second positions of the side surfaces of
The optical fiber strands up to the n-th one were closely fixed to the n-1 position on the side surface of each optical fiber, and each of the optical fiber strands was heated simultaneously at each position to make them stick to each other. A method for manufacturing an optical fiber star coupler, which comprises fusing optical fiber strands, and further simultaneously stretching all the fused portions of the optical fiber strands while maintaining the softened state of each of the optical fibers. is provided.

The optical fiber star coupler according to the present invention basically consists of three
The structure is similar to that of a conventional optical fiber star coupler in that a dB optical coupler is coupled into multiple throws to achieve a large number of branches. However, the optical fiber star coupler according to the present invention differs significantly in that there are no optical fiber coupling points between each 3 dB coupler.

That is, since there is no coupling point of the optical fiber, frequent occurrence of local breakage is avoided, and there is no variation in branching ratio due to splice loss at the coupling point. Moreover, if manufactured according to the manufacturing method according to the present invention described later, each 3
The extra length of the optical fiber line connecting the dB optical couplers can be shortened to the maximum, and the overall size of the optical fiber star coupler can be reduced.

The output signal from this optical fiber star coupler passes through three stages of 3 dB optical fiber couplers, so it is essentially 9 dB.
There is a reduction in the power of B, but the only other propagation loss is the insertion loss of the optical fiber itself. The insertion loss of an optical fiber coupler fabricated by the fusion-stretching method using optical fibers is described in the document “Fiber Cup Rough Applications with Automatic Fusion Elongation” by I, Yokohama (I, Yokohama).
Process is (Fiber Coupler Fabr
cation with AutomaticFus
ion-Blongation Processes
) (OFS'October 8, 1986 (OFS'
86. 10.8)), but generally 0.
It is 1 dB or less.

Furthermore, although the details will be described later, according to the manufacturing method according to the present invention, the most labor-intensive fusion and stretching process in the manufacture of a 3dB optical fiber coupler is performed on a plurality of fused and stretched parts at once. Therefore, the time required for production is greatly shortened, and at the same time, the optical properties of each welded and stretched portion are well matched.

Although a star coupler that branches an input signal into a plurality of signals of equal power will be described here, including the embodiments described later, it is also possible to adopt a configuration in which the output (optical power) differs depending on the output terminal. Further, it is also possible to impart wavelength selectivity to the fusion/stretching section which is an optical coupler.

EXAMPLES The present invention will be described in more detail with reference to the drawings below.
What is disclosed below is only one example of the present invention, and does not limit the technical scope of the present invention in any way.

FIG. 1(a) is a perspective view showing the appearance of an optical fiber star coupler manufactured according to the present invention.

That is, this optical fiber star coupler has one input 1
00 and eight outputs 101-108, 3dB
Fusion/stretching section 111.121.122 responsible for branching operation.
131.132.133.134 are in the X-axis direction on the coordinates shown in the figure, that is, parallel to the longitudinal direction of the optical fiber, and the line connecting the centers of the fused and stretched parts is in the yldi direction, that is, The optical fibers are arranged parallel to each other in a direction perpendicular to the longitudinal direction of the optical fiber.

FIG. 1(5) shows the optical fiber star coupler shown in FIG. 1(a) expanded in the y-axis direction, making it easier to understand the configuration as an optical circuit.

In addition, in this figure, each fused/stretched part 111.121.12
2.131.132.133.134 each input C1
The output is shown as aSb.

As shown in FIG. 1(c), the optical signal input from the input 100 enters the first stage fusion/stretching section 111 from C, is split into two, and is output from a and b. Ru.

Subsequently, each optical signal is transferred to the second stage fusing/stretching section 121.1.
22, each from C, branches into two, and each a
, b. Furthermore, this optical signal is sent to the third-stage fusion/stretching section 131, 132, 133, and 134, respectively.
, each branches into two and outputs 101 to 10.
8 is output.

Here, when comparing this optical fiber star coupler with the conventional optical fiber star coupler shown in Fig. 4, the total length of the branch circuit is approximately 1/3 in the X direction, and each fusion Since there is almost no excess fiber between the extensions, the overall dimensions are extremely small.

Further, according to the manufacturing method of the present invention described later, in this optical fiber star coupler, input 100 → fusion/stretching section 111 (c-b) - fusion/stretching section 122 (c-
The optical transmission path from a) → fused/stretched section 134 (C-a) → output 107 is formed by one continuous optical fiber, and similarly, the fused/stretched section 111a → fused/stretched
Stretching part 121 (C-b) → Fusion/stretching part 131 (C-b
) → Optical transmission line of output 102, fused/stretched part 121a → fused/stretched part 132 (c-b) → Transmission path of output 104 and fused/stretched part 122b → fused/stretched part 133 (c-
The optical transmission paths of a)→output 105 are all formed by one continuous optical fiber. In other words, each fused/stretched part 111.121.122.131.132
．． 133 and 134 are both connected without any joining parts by processing. As mentioned in the previous section, the insertion loss of the optical fiber itself is about 0.1 dB at most, so the insertion loss of the entire optical fiber star coupler mentioned above is the sum of the insertion loss of the three stages of branching and the optical fiber itself. The total sum is 9.36B or less. In addition, each output 101 to 10
The optical output power at 8 is also uniform at 9.2 dB±0.1 dB.

Now, a method of manufacturing the optical fiber star coupler as described above will be explained below.

FIGS. 2(a) to 2(d) are diagrams illustrating the configuration of a jig for manufacturing the above-described optical fiber star coupler and its usage method.

This jig has a guide member 20 as shown in FIG. 2(a).
A pair of stretching tables 210 and 220 are placed on the paper. The stretching tables 210 and 220 are movable along the guide member 200 and away from each other and the screws 20
1.202, it can also be fixed in the position shown in FIG. 2(a). Further, each of the stretching tables 210, 220 is provided with a row of mutually parallel pins 211, 212, 221, 222 consisting of eight pins a to h on its upper surface, and as will be described later, these pins are connected to each other. By inserting an optical fiber between them, the optical fiber can be positioned in the horizontal direction.

In the device in this example, the diameter of each pin is 500 μm.
In each row, the center distance of the pins is 6
30μm, i.e. 13mm between the pins.
They were arranged in a straight line so that there was a gap of 0 μm. Also,
The distance between the rows 211 and 212 or 221 and 222 is lQmm, and the height of each pin a-h is 2m.
It was set as m.

These pins are used to position the optical fibers so that they are parallel to each other and to stack them one above the other without misalignment, as will be described later. Further, consideration should be given to alleviating bending stress caused by the curvature of the folded portion of the optical fiber. Furthermore, instead of using pins, a structure in which the optical fiber is embedded in a groove cut on the stretching table can function in the same way.

Next, a method of using the above-mentioned jig will be explained. still,
The optical fiber used in the following operations has at least the protective coating removed from the portion to be processed, leaving only the core and cladding.

First, as shown in FIG. 2, for example, four optical fibers 301a-b to 304a-b are arranged so that one optical fiber passes between the pins in each row.

Next, as shown in FIG. 2(C), the optical fibers with the second grain are passed between the pins in each row.
Further, four optical fibers 311a-b to 314a-b are arranged in close contact with each other on the optical fibers 301a-b to 304a-b.

There are many possible combinations of optical fiber arrangements at this time, but at least one of the ends of the four arranged optical fibers is the input end of the completed optical fiber star coupler (this example In this example, this corresponds to the optical fiber 301a on the left side of FIG. 2(b)), and at least eight output ends (in this example, the optical fibers 301b to 304b and 311b to 314b on the right side of FIG. 2(C)
corresponds to this), so it is necessary to take this point into consideration.

That is, as will be described later, two stages of optical fibers are fused and stretched between the rows of pins 212 and 221 to form an optical branching section. Therefore, in contrast to FIG. 1(b), the optical fibers t to Z in this section shown in FIG.
．． It corresponds to 133.134. In addition, in FIG. 2(b), on the stretching table 220, between pins a and b, pin b11
! : Between C, between pins f and g, between pins g and h,
Optical fibers 304b and -303b respectively pass through.

302b and 301b, in contrast to FIG. 1(b),
They correspond to outputs 102.104.105.107, respectively. Furthermore, in FIG. 2(C), the optical fiber 304b
, 303b, 302b, 301b, the optical fibers 311b, 312b, 313b are disposed above them.

314b has an output of 1, respectively, in contrast to FIG.
It corresponds to the old 103.106.108.

In addition, in order to meaningfully combine the fused and stretched portions formed by the optical fibers t - z shown in FIG. are doing. In this embodiment, in the state shown in FIG. 1(b), from between pins b and c on the stretching table 210 to pin c
Folding of the optical fiber between pins d, folding of the optical fiber from between bins b and c to between pins c and d, and folding of the optical fiber from between pins d and e to between bins e and f on the stretching table 220 The folding of the optical fiber corresponds to three of these. Also,
In the state shown in FIG. 1(C), the optical fiber is folded back on the stretching table 210 from between pins b to between pins c and d, and the optical fiber is folded from between pins e and f to between pins f and g. The remaining three portions correspond to folding back and folding back the optical fiber from between pins c and d to between pins d and e on the stretching table 220.

The curvature of the folded portion of the optical fiber shown in Figure 2 Q)) and (C) prevents an increase in loss or breakage due to bending of the optical fiber, and at the same time reduces twisting, deflection, bending, etc. of the optical fiber. Therefore, the curvature is actually 10m.
An extra length was given so that it was at least m.

The optical fibers 301 to 304 and 311 to 314 arranged in this way are connected to at least the rows of pins 211 and 221.
A tension control device (not shown) is used to apply a constant tension in the range of 0.5 g to 50 g to prevent bending between the two, and
In order to maintain this state, it is fixed on the guide member 200 with an adhesive 402, as shown in FIG. 2(6). Furthermore, weights 213 and 223 are respectively placed between the rows of pins 211 and 212 and between the rows of pins 221 and 222 to bring the vertically overlapping optical fibers into close contact.

FIG. 3 is a diagram illustrating the process of fusing and stretching the optical fibers arranged as described above. Note that FIG. 3 shows substantially the same thing as shown in FIG. 2 (6), but the scale is different from that of FIG. 2 (6).

First, while the light emitting element 500 is arranged at the end of the optical fiber 301a, for example, the optical fibers 301b and 314b
Light-receiving elements 501 and 502 are also arranged at the ends of each of. These elements are processed in the fusing/stretching process described below.
This is for monitoring the mutual coupling state of optical fibers.

Subsequently, each optical fiber is heated and melted by heating means placed between the drawing tables 210 and 220. As described above, since each optical fiber is in close contact with each other in this portion, the optical fibers that are in close contact with each other from above and below are fused to each other. Therefore, while maintaining the softened state of the optical fiber by adjusting the amount of heating,
While loosening the screws 201 and 202, the stretching tables 210 and 220 are moved along the guide member 200 with a traction force of 1 g to 10 g so that it moves away from each other.

As shown in FIG. 2 et al., the optical fibers 301a and 30
1b are both ends of one continuous optical fiber, and at the beginning of the above operation, almost all the optical signal injected into the optical fiber 301a by the light emitting element 500 is transferred to the optical fiber 30.
1b. As the stretching progresses, optical coupling occurs at the fused/stretched portion of the optical fiber, and optical output also appears in the optical fiber 314b. Therefore, the light receiving element 502
The stretching is stopped when the output of the optical fiber 314b, as detected by , reaches a desired amount.

Needless to say, at this time, the optical fibers t-z are simultaneously fused and drawn under the same conditions.

In this way, an optical fiber star coupler as shown in FIG. 1(a) is completed. Note that this optical fiber star coupler is actually put into practical use by being housed in a protective container.

As a result of measuring the branching ratio of the optical fiber star coupler manufactured in this way, the loss value at each of the 8 branching ends was as follows.
It was in the range of 9.1±0.05 dB, and each fused/stretched part was under uniform conditions.

In other words, it has been found that it is not necessary to monitor the stretching process by injecting light as described above for all output optical fibers.

In this example, an optical fiber star coupler was fabricated using an optical fiber from which the protective coating had been removed in advance, but the protective coating only needs to be removed from the fused/stretched portion, and the optical fiber is not fixed to the jig. After that, the protective coating may be removed only at the fused/stretched portions using chemicals or the like.

Further, the arrangement of the optical fibers is not limited to this embodiment, and further, the vertical relationship of the arranged optical fibers may be arbitrarily changed at the folded portion.

Further, in this embodiment, an eight-branch type optical fiber star coupler and a method for manufacturing the same have been described, but the present invention is not limited thereto. That is, not only optical fiber star couplers with 2h branches such as 4 branches, 16 branches, 32 branches, 64 branches, 128 branches, etc., but also optical fiber star couplers with any other number of branches or arbitrary branch ratios are also applicable. This can be realized according to the present invention.

Effects of the Invention As detailed above, in the optical fiber star coupler according to the present invention, a plurality of 3 dB optical couplers forming the star coupler are integrally molded without any negative coupling. Therefore, frequent breakage at the joints, such as in conventional star couplers, is avoided, and variations in connection loss at the joint points are not possible. Further, the insertion loss consists only of the essential loss caused by the 3 dB optical coupler and the propagation loss that the optical fiber itself has.

In addition, since this optical fiber star coupler does not require coupling of 3 dB optical fiber couplers during manufacture, the optical fibers that connect each 3 dB optical coupler can be shortened to the maximum, and the overall dimensions of the optical fiber star coupler can be reduced. It has been miniaturized.

Furthermore, according to the manufacturing method of the present invention, this optical fiber star coupler can perform the most time-consuming fusion and stretching process in the production of 3dB optical fiber couplers at once for multiple fused and stretched parts. , the time required for production is shortened, and at the same time, the optical properties of each welded and stretched portion are well matched.

Due to these features, the optical fiber star coupler according to the present invention can significantly reduce manufacturing time compared to conventional products, and also exceeds conventional products in terms of quality and yield.
Achieve a mass supply of low-priced, high-quality optical fiber star couplers. That is, the role played by the present invention in the field of various optical communication technologies such as optical CATV is immeasurable.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams showing the appearance and optical structure of an optical fiber star coupler according to the present invention, respectively, and FIGS. 2(a) to (6) are diagrams showing the optical fiber star coupler according to the present invention. FIG. 4 is a diagram illustrating the configuration of an apparatus for carrying out the method for manufacturing a fiber star coupler and its usage method; FIG. 6 is a diagram showing the structure of an optical fiber star coupler, and FIGS. 5(a) to 5(C) are diagrams showing an optical fiber coupler, which is a member of a conventional optical fiber star coupler, and a method for manufacturing the same. FIG. FIG. 5 is a diagram illustrating a device for manufacturing the optical fiber coupler shown in FIG. 5(C) and a method of using the same. [Main reference number] 40...Input 41, 42.43.44.45.46.47...3d
B optical coupler, 41a, 42a, 43a, 44a, 45a,
46a, 47a. ...Connection part, 41b, 42b, 43b, 44b, 45b,
46b, 47b. ... extra length fiber, 51, 52.53.54.55.56.57 ... output, 81, 82 ... optical fiber, 84 ... core, 85 ... cladding, 91.
92... Optical fiber, 93a, 93b, 94a, 94b... Fixing device, 9
5a, 95b...Stretching table, 96a, 96b...Pin, 97a, 97b...Horizontal position adjustment device, 98a
, 98b... Vertical position adjustment device, 100... Input, 101, 102, 103.104.105.106.1
07.108...Output, 111, 121.122.131.132.133.1
34... Fusion/stretching part, 200... Guide member, 201.202... Screw, 2
10, 220... Stretching table, 301a-b, 302a-b, 303a-b, 3
04a-b. 311a-b, 312a-b, 313a-b, 3
14a-b. ...Optical fiber, 500...Light emitting element, 501.502...Light receiving element, 600...Heating means patent applicant Nippon Telegraph and Telephone Corporation Agent Patent attorney Masahiko Nii (b) 100. ...Input 101-108...
Output 111.121.122, 131.132, 133
, 134...Full chopsticks, stop extension part M 'J'
lr';r IJJFigure 5

Claims (8)

[Claims] (1) The input of the first stage optical coupler is an input from the outside, the output of the first stage optical coupler is the input of the second stage optical fiber coupler, and the first stage optical coupler is an input from the outside. The output of the coupler is the input of the i+1st stage optical fiber coupler, and the output of each n-1st stage optical fiber coupler is the output to the outside, and the total number of branches is 2^n.
A method for manufacturing an n-1 stage optical fiber star coupler, the method comprising: closely contacting a side surface near an end of a second optical fiber to a first position on a side surface of a first optical fiber strand; and fixing third and fourth optical fibers at respective second positions on the side surfaces of the first and second optical fibers on the same side with respect to the first position.
The side surfaces near the ends of the optical fiber strands are closely attached to each other, and the optical fiber strands up to the n-th, which are closely fixed to the n-1th position on the side surface of each optical fiber, are closely fixed, At each of the positions, each of the optical fiber strands is simultaneously heated to fuse the optical fiber strands that are in close contact with each other, and further, while maintaining the softened state of each of the optical fibers, the optical fiber strands are heated. A method for manufacturing an optical fiber star coupler, characterized in that all fused parts are stretched at the same time. (2) The method for manufacturing an optical fiber star coupler according to claim 1, wherein the first to n-1th positions are arranged on the same plane. (3) Between the first to n-1th positions, each of the optical fibers is bent so as to reverse the propagation direction of light by 180°, and the first to n-1st positions are The method for manufacturing an optical fiber star coupler according to claim 1, wherein the optical fiber star couplers are arranged on one predetermined straight line. (4) 1 movable in a direction perpendicular to the line arranged in the first to n-1th positions in a direction that moves away from each other;
The method for manufacturing an optical fiber star coupler according to claim 3, characterized in that the optical fiber strands before and after the first to n-1 positions are respectively fixed on a pair of supporting means. . (5) In the stretching operation, a predetermined optical signal is injected from one end of any one of the optical fibers, and the other end of the optical fiber and the same optical fiber that is fused to the optical fiber are A light receiving element is placed on each side edge,
2. The method of manufacturing an optical fiber star coupler according to claim 1, wherein the stretching step is terminated when the optical power detected by the light receiving element reaches a predetermined value. (6) The input of the first-stage optical coupler is an input from the outside, the output of the first-stage optical coupler is the input of the second-stage optical fiber coupler, and the The output of the optical fiber coupler is the input of the i+1st optical fiber coupler, and the output of each optical fiber coupler of the n-1st stage is the output to the outside, and the total number of branches is 2.
n-1 stages of optical fiber star couplers, each of the optical fiber couplers having a side surface of a first optical fiber strand adjacent to an end of a second optical fiber; each of the continuous optical couplers shares one continuous optical fiber as the first optical fiber or the second optical fiber. Optical fiber star coupler featuring: (7) The optical fiber according to claim 6, wherein the optical fibers connecting the continuous optical fiber couplers are each bent so that the propagation direction of the optical signal is reversed by 180 degrees. Fiber star coupler. (8) The optical fiber star coupler according to claim 7, wherein the optical fiber couplers are arranged in parallel on a straight line perpendicular to the propagation direction of the optical signal.